Indexing mechanism



March 3,1942. F L, REA 2,275,286

INDEXING MECHANISM Filed Nov 110, 194C WSW l9 Patented Mar. 3, 1942 sraUiTED INDEXING MEC'HANISl /l Frederick L. Creager, Camden, N. J.,assignor to Radio Corporation of America, a corporation of DelawareApplication November 3c, 1940, Serial No. 367,880

6 Claims. on. 74-10)- The invention relates to indexing mechanisms forachieving the rapid and accurate setting of a dial, such, for example,as the tuning dial of a radio set. Considered from one aspect theinvention herein disclosed constitutes an improvement upon the inventionmore broadly claimed in the copending application of Wendell L. Carlson,Serial No. 352,509, filed August 14, 1940.

The prior art discloses several indexing mechanisms comprising a, pawland a main or auxiliary dial plate provided with detents or notcheswhich are individual to the more frequently dial settings, and which areselectively engaged by the pawl when the desired setting is achieved.Thus, if the pawl is attached to a knob it may be moved rapidly over thedial plate to the approximate setting desired whereupon the pawl engagesthe detent individual to that setting and the operator is advised by hissense of touch that an exact setting has been achieved.

The principal objection to the indexing mechanisms of the early priorart is that they either required at least partial disassembly of theradio or other apparatus during the setting-up process, or wereotherwise so complicated in their adjustment as to inhibit their use byan unskilled operator. As to the above, see, by way of example, WirelessWorld (British) February 9, 1927, page 162; see also U. S. Patent1,964,449.

The foregoing and other objects to the indexing mechanisms of the earlyprior art substantially obviated in accordance with the above identifiedCarlson disclosure by the use of a dial plate constituted of arelatively soft metal, such, for example, as copper, brass, or the like,and by making the detents or notches individual to the several settingstherein as by a punch, thrust, or other force applied to the said softmetal plate, either (a) by means of a separate tool inserted through ahole provided for that purpose in the dial knob or (b) by means of awedge-shape detent-fcrming element carried behind the control panel onthe free end of a flat spring which, when pressed downwardly, as bymeans of a cam controlled by a separate knob on the front panel, andsuddenly released, imparts the requisite force to the wedge-shapeelement.

One objection to the first (a) of the above described arrangements isthat the intensity of the force applied to the indexing plate is left tothe judgment and skill of the person making the set-up; further, theseparate punch or other tool may become lost or mislaid. The second (b,above) arrangement has proven, in some instances, to be unsatisfactorysince the very pres- 56 once of an auxiliary knob on the control panelappears to prompt even those familiar with its purpose to fiddle with itso that in some instances detents have been set up on the indexing plateat points where no station in fact exists.

Accordingly, the principal object of the present invention is to providean improved indexing mechanism which may be set up without the use ofseparate tools and wherein the setting-up ele- -ment, though permanentlyattached and readily accessible, is concealed from the unitiat'ed orcasual operator of the radio or other apparatus with which the indexingmechanism is associated.

Other objects and advantages will be apparent and the invention itselfwill be best understood by reference to the following specification andto the accompanying drawing, wherein Figure 1 is a front elevationalView of a radio tuner incorporating an indexing mechanism constructed inaccordance with the principle of the invention, and

Figures 2, 3 and 4 are sectional views taken on the similarly numberedsection lines of Fig. 1.

In the drawing, wherein like reference characters designate the sameparts in all figures, 5 designates an opening in the control panel 1 ofa radio cabinet within which a main tuning shaft 9 is mounted. Shaft 9extends through a support H and through a concentrically mountedcircular dish or plate 13 which may be conveniently secured to thesupport If as by studs l3s. Plate if: has an outwardly turned rim l5constituted of copper, brass or other relatively soft metal whichpreferably extends into or through .the opening 5 in the panel 1 andterminates adjacent the plane of the front surface of said panel.

The main tuning shaft 9 is susceptible of rotation under the control ofa knob l9 which may be provided with a hub Illh within which thepreferably flattened end 96 of the tuning shaft 9 is seated. Thediameter of the knob It, the length of the shaft 9, and the depth of theopening in the hub 1% in which the shaft end 96 is received arepreferably such that when the knob is mounted in position, the outeredge of its rear surface will be spaced slightly in front of theoutwardly turned soft metal rim E5 on the stationary plate I3.

There is a strip 2| constituted of spring metal affixed adjacent itscenter to the rear surface of the knob I9 as by screws 2ls arrangedabout the hub l9h. The free end of the spring metal strip which isdesignated Zia extends into the clearance space between the rear surfaceof the knob l9 and the edge of the soft metal rim I5, and is provided,within the said space, with a wedgeshape projection 23 which is biased(by its spring support) inwardly against the rim I so that, as the knobis rotated, it will ride on the rim and follow any detents which may beprovided in the surface thereof. The opposite end Zlb of the springmetal strip terminates at a point adjacent, but not touching, the innerside surface circumference of the rim I5. Since the strip 2| isconstituted of spring metal, it is obvious that any force exerted uponits free end 21b and tending to extend it inwardly in the direction ofthe plate I 3 will be opposed by the counter or biasing force of thestrip.

The outer surface of the knob I9 is provided with a protuberance 25which extends across the knob along substantially the same diameter asthe spring metal strip 2| on the opposite or inner knob surface. Thelong sides of this protuberance 25 will ordinarily be grasped by theoperators fingers in manipulating the knob during the tuning operation.There is a central, relatively narrow, slot 2'! running the full lengthof the protuberance 25 and within which a trip blade or lever arm 29 ismounted as on a pivot or fulcrum 3| adjacent the rear surface of theknob in the space between the hub 19h and the free end 2|b of the spring2|. The exposed edge of the lever arm 29 is preferably of a contoursimilar to that of the protuberance 25 and is preferably flush with thetop surface thereof throughout a greater portion of its length, so that,to a caual observer, the said exposed edge of the lever appears tocomprise merely a pointer for the scale 33 which surrounds the knob.(The pointer-like appearance of the exposed surface of the lever isenhanced when the said surface comprises a bright metal.) However, thatend of the lever arm 29 which lies on the upper half of the knob l9 (i.e. opposite the half containing the pivot 3|) is provided with a lip 29awhich extends beyond the surface of the protuberance 25 and which may beengaged by the operator's finger or fingers to move the lever arm in thedirection of the curved arrow 29b in Fig. 2.

As the lip 2% is pulled outwardly, the lever 29 will pivot on thefulcrum 3| and its opposite end 290 will be moved inwardly against thebiasing force of the spring-end Zlb. If the lip 29a is then suddenlyreleased, that part of the edge of the lever which lies beneath the lipwill be projected against the wedge-shaped element 23 by the forceapplied to the opposite end 290 of the lever by the release of theenergy stored in the spring at Mb, and a detent I5b (Fig. 3) will beformed in the soft metal rim H5 at a point thereon corresponding to thedial or pointer setting at the time the lever is released. Thus to setupa station on the indexing mechanism, it is merely necessary to rotatethe knob l9 until the desired station is tuned in, pull out the free-end29a of the lever, and then permit it to fly back.

Since, as previously pointed out, the wedgeshaped element 23 is normallybiased (as by the spring 2m on which it is mounted) against the rim l5,it serves as a pawl, which, in engaging a detent in the rim during thetuning operation, advises the operator through his sense of touch that adesired station setting has been achieved.

In the embodiment of the invention which has been selected forillustration, a single strip (2|) of spring material serves, in theinterests of simplicity, both as the biasing means for returning thelever 29 to its idle position and as a mount for the detent-formingwedge-shaped pawl 23. Obviously, however, separate springs may beprovided if desired. Other modifications of the invention, such, forexample, as the elimination of the protuberance 25 on the knob 19 (inwhich event the lever arm 23 may be mounted flush with the principalsurface of the knob) will suggest themselves to those skilled in theart. It is to be understood, therefore, that the foregoing is to beinterpreted as illustrative and not in a limiting sense except asrequired by the prior art and by the spirit of the appended claims.

What is claimed is:

1. In combination, a rotatable shaft, a stationary index memberconstituted of an easily deformed material mounted about said shaft, acontrol member mounted on the end of said shaft in front of said indexmember, and means mounted on said control member for applying adeforming force to said indexing member.

2. In combination a rotatable shaft, a stationary index memberconstituted of an easily deformed material mounted about said shaft, aknob mounted on the end of said shaft in front of said index member, andmeans comprising a spring-actuated lever for applying a deforming forceto said index member.

3. The invention as set forth in claim 2 and wherein said lever liesadjacent the face of said knob and comprises a pointer for indicatingthe setting of said rotatable shaft.

4. In combination, a rotatable shaft, 2. stationary index plateconstituted of an easily deformed material and a scale bothconcentrically mounted about said shaft, a knob mounted on the end ofsaid shaft in front of said index plate, a pointer mounted on said knoband adapted to be read in connection with said scale, and meanscomprising said pointer for applying a deforming force to said indexplate at a point thereon corresponding to the point indicated on thescale by said pointer.

5. In combination, a rotatable shaft, a stationary index memberconstituted of an easily deformed material mounted about said shaft, aknob mounted on the end of said shaft in spaced relation with respect tosaid index member, a wedge-shaped pawl mounted adjacent the innersurface of said knob and biased to bear against said index member, and alever mounted on said knob for applying a deforming force to said indexmember through said wedge-shaped pawl.

6. The invention as set forth in claim 5 and wherein a spring mounted onsaid knob adjacent the fulcrum end of said lever supplies said deformingforce.

FREDERICK L. CREAGER.

